1. Field of the Invention
The present invention relates to an air conditioner for vehicles for performing cooling and heating in a passenger cabin of the vehicle, and particularly to an air conditioner which is useful in electric automobiles and the like.
2. Description of the Related Art
An air conditioner of a heat pump type is generally used in vehicles such as electric automobiles which have no internal heat source such as an internal combustion engine. Such an air conditioner comprises mainly a compressor, a four-way valve, an exterior heat exchanger, expansion means and an interior heat exchanger. The interior heat exchanger is interchangeably used as a heat absorber or a heat radiator by means of refrigerant cycles using the four-way valve, to perform cooling and heating in the vehicle cabin.
Basically, the conventional air conditioner described above can perform operations only in a cooling mode and a heating mode. Thus, drawbacks arise in that poor visibility is apt to occur on the window glass of the vehicle when performing heating under high humidity such as during rain or snow. Further, dew deposited on the interior heat exchanger evaporates upon changeover from cooling to heating, resulting in similar poor visibility as described above. Further, a drawback arises in that the blowing air temperature of the air conditioner is inevitably lowered even during dehumidification, and comfort to the passengers is greatly impaired.